#include <stdio.h>
unsigned int Gcd(unsigned int a,unsigned int b)
{
    unsigned int r,max,min;
    max=a>=b?a:b;
    min=a<b?a:b;
    r=max%min;
    if(0!=r)
    {
        return Gcd(r,b);
    }
    else
        return min;
}
void main()
{
    unsigned int a,b;
    printf("Input two numbers:");
    scanf("%u,%u",&a,&b);
    printf("the greatest common divisor is %u",Gcd(a,b));
}
